Re: Database design

x schrieb:
> "Alexandr Savinov" <spam_at_conceptoriented.com> wrote in message
> news:43fc6eec$1_at_news.fhg.de...

>> x schrieb:

>>> Do you know about any published academic paper about relational

>>> which the term flat is defined  ?
>>> Why is it useful to define this term from a scientific point of view ?
>> There is several reasons why it is useful:

>> 1. It allows us to get an informal impression and what is the essence,
>> what we are talking about. An informal characterization (an idea) is the
>> primary thing while formalities is the secondary thing (a tool which
>> makes it easier to derive consequences).

>> 2. Just because we use other informal terms in order to describe a
>> theory or approach. Eventually, in any academic paper and in this group
>> most of words have no formal definition. And this does not prevent us to
>> comprehend them. And again: writing formulas does not add a value to any
>> theory - it is only a form which may make it easer or more difficult to
>> understand.

>> 3. This group is intended to discuss what is not covered by academic
>> papers so there is nothing bad that we can introduce something unusual.

>> Anyway, I do not understand why a structure without an order (hierarchy,
>> multiple levels, depth etc.) cannot be characterized as flat? It is
>> rather precise characterization (in contrast to many terms from academic
>> papers which are frequently simply misleading).

Because what you wrote is actually a definition of being flat:

Space (say, 2-dimensional Euclidean space) Point (in this space, as a combination of 2 coordinates) Coordinate (a projection of the point on some axis)

Since there is no continuation (this space is not nested) we say it is flat. We can build a non-flat space if assume that coordinates are themselves points with their own coordinates. Those coordinates could also be points with their own coordinates and so on. Alternatively, we can continue this space hierarchy in the opposite direction (upward). The points from this set can be used as coordinates for points from another set. Those points can again be used as coordinates.

So we call a structure flat if it can be shown equivalent to a n-dimensional space (without a hierarchy).

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